bsnl broadband dns servers- why open dns sucks for bsnl broadband

If you have problem loading a webpage or website ,the primary culprit for this might be the d-n-s provided by bsnl. But you have to remember that changing these servers CANNOT improve your dowload speed ,it just improves the loading time of a webpage.I have read somewhere that changing your default bsnl broadband dns servers to that of open dns servers, will greatly improve your download speed,this is completely false and untrue .Infact if you use open dns servers,it will actually decrease your bsnl broadband speed.This is because open dns do not have servers in india, it is actually in some place else.And the time it takes to connect to that place will be enough for us to load a webpage in normal bsnl broadband dns servers.Yet still bsnl broadband dns servers suck , that is why ,everyone recommends other dns servers.
Just wanted to clear that up.....